6-demicube
Uniform 6-polytope From Wikipedia, the free encyclopedia
In geometry, a 6-demicube or demihexeract is a uniform 6-polytope, constructed from a 6-cube (hexeract) with alternated vertices removed. It is part of a dimensionally infinite family of uniform polytopes called demihypercubes.
Demihexeract (6-demicube) | ||
---|---|---|
![]() Petrie polygon projection | ||
Type | Uniform 6-polytope | |
Family | demihypercube | |
Schläfli symbol | {3,33,1} = h{4,34} s{21,1,1,1,1} | |
Coxeter diagrams | ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]()
| |
Coxeter symbol | 131 | |
5-faces | 44 | 12 {31,2,1}![]() 32 {34} ![]() |
4-faces | 252 | 60 {31,1,1}![]() 192 {33} ![]() |
Cells | 640 | 160 {31,0,1}![]() 480 {3,3} ![]() |
Faces | 640 | {3}![]() |
Edges | 240 | |
Vertices | 32 | |
Vertex figure | Rectified 5-simplex![]() | |
Symmetry group | D6, [33,1,1] = [1+,4,34] [25]+ | |
Petrie polygon | decagon | |
Properties | convex |
E. L. Elte identified it in 1912 as a semiregular polytope, labeling it as HM6 for a 6-dimensional half measure polytope.
Coxeter named this polytope as 131 from its Coxeter diagram, with a ring on one of the 1-length branches, . It can named similarly by a 3-dimensional exponential Schläfli symbol or {3,33,1}.
Cartesian coordinates
Cartesian coordinates for the vertices of a demihexeract centered at the origin are alternate halves of the hexeract:
- (±1,±1,±1,±1,±1,±1)
with an odd number of plus signs.
As a configuration
This configuration matrix represents the 6-demicube. The rows and columns correspond to vertices, edges, faces, cells, 4-faces and 5-faces. The diagonal numbers say how many of each element occur in the whole 6-demicube. The nondiagonal numbers say how many of the column's element occur in or at the row's element.[1][2]
The diagonal f-vector numbers are derived through the Wythoff construction, dividing the full group order of a subgroup order by removing one mirror at a time.[3]
D6 | ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() | k-face | fk | f0 | f1 | f2 | f3 | f4 | f5 | k-figure | notes | |||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
A4 | ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() | ( ) | f0 | 32 | 15 | 60 | 20 | 60 | 15 | 30 | 6 | 6 | r{3,3,3,3} | D6/A4 = 32*6!/5! = 32 |
A3A1A1 | ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() | { } | f1 | 2 | 240 | 8 | 4 | 12 | 6 | 8 | 4 | 2 | {}x{3,3} | D6/A3A1A1 = 32*6!/4!/2/2 = 240 |
A3A2 | ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() | {3} | f2 | 3 | 3 | 640 | 1 | 3 | 3 | 3 | 3 | 1 | {3}v( ) | D6/A3A2 = 32*6!/4!/3! = 640 |
A3A1 | ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() | h{4,3} | f3 | 4 | 6 | 4 | 160 | * | 3 | 0 | 3 | 0 | {3} | D6/A3A1 = 32*6!/4!/2 = 160 |
A3A2 | ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() | {3,3} | 4 | 6 | 4 | * | 480 | 1 | 2 | 2 | 1 | {}v( ) | D6/A3A2 = 32*6!/4!/3! = 480 | |
D4A1 | ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() | h{4,3,3} | f4 | 8 | 24 | 32 | 8 | 8 | 60 | * | 2 | 0 | { } | D6/D4A1 = 32*6!/8/4!/2 = 60 |
A4 | ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() | {3,3,3} | 5 | 10 | 10 | 0 | 5 | * | 192 | 1 | 1 | D6/A4 = 32*6!/5! = 192 | ||
D5 | ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() | h{4,3,3,3} | f5 | 16 | 80 | 160 | 40 | 80 | 10 | 16 | 12 | * | ( ) | D6/D5 = 32*6!/16/5! = 12 |
A5 | ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() | {3,3,3,3} | 6 | 15 | 20 | 0 | 15 | 0 | 6 | * | 32 | D6/A5 = 32*6!/6! = 32 |
Images
Coxeter plane | B6 | |
---|---|---|
Graph | ![]() | |
Dihedral symmetry | [12/2] | |
Coxeter plane | D6 | D5 |
Graph | ![]() |
![]() |
Dihedral symmetry | [10] | [8] |
Coxeter plane | D4 | D3 |
Graph | ![]() |
![]() |
Dihedral symmetry | [6] | [4] |
Coxeter plane | A5 | A3 |
Graph | ![]() |
![]() |
Dihedral symmetry | [6] | [4] |
Related polytopes
Summarize
Perspective
There are 47 uniform polytopes with D6 symmetry, 31 are shared by the B6 symmetry, and 16 are unique:
The 6-demicube, 131 is third in a dimensional series of uniform polytopes, expressed by Coxeter as k31 series. The fifth figure is a Euclidean honeycomb, 331, and the final is a noncompact hyperbolic honeycomb, 431. Each progressive uniform polytope is constructed from the previous as its vertex figure.
It is also the second in a dimensional series of uniform polytopes and honeycombs, expressed by Coxeter as 13k series. The fourth figure is the Euclidean honeycomb 133 and the final is a noncompact hyperbolic honeycomb, 134.
Skew icosahedron
Coxeter identified a subset of 12 vertices that form a regular skew icosahedron {3, 5} with the same symmetries as the icosahedron itself, but at different angles. He dubbed this the regular skew icosahedron.[4][5]
References
External links
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